This invention relates to novel, high performance solvent compositions which can be used safely in aerosol applications for cleaning surfaces, such as metal surfaces.
Recently, n-propyl bromide has been shown to be an excellent substitute for chlorinated hydrocarbons as a cleaning and degreasing solvent.
U.S. Pat. No. 5,707,954 describes stabilized degreasing and cleaning solvent compositions which are comprised of at least 90 wt % of n-propyl bromide and a 1,4-dioxane-free stabilizer system which comprises 2,2-dialkoxypropane. The stabilizer system may contain in addition a nitroalkane, nitrobenzene, an epoxide such as 1,2-epoxybutane, and/or an amine. Efficacious results are shown in the example wherein a solvent composition was composed of the following ingredients: 96.5 wt % of n-propyl bromide, 2.5 wt % of 2,2-dimethoxypropane, 0.5 wt % of 1,2-epoxybutane, and 0.5 wt % of nitromethane. The patent also describes, inter alia, tests involving replacement of the 2.5 wt % of 2,2-dimethoxypropane by 2.5 wt % of 1,3-dioxolane or 2.5 wt % of 1,4-dioxane.
In one of its aspects, this invention involves the surprising discovery that when certain weight ratios of certain flammable additive components are blended in n-propyl bromide, the components can actually function as flame retardants or flame suppressants when the resulting composition is used in aerosol applications. Thus, even though the composition is in a highly dispersed or aerosol statexe2x80x94a condition which normally engenders increased flammabilityxe2x80x94the composition is more flame resistant than if the particular flammable additive ingredients had not been blended in the n-propyl bromide.
Another aspect of this invention is the discovery that certain very small amounts of flammable additives when blended in n-propyl bromide provide suitably effective stabilization against metallic corrosion even at mildly elevated temperatures. Indeed, this advantageous result can be achieved by use of very small concentrations of but two additives in the n-propyl bromide.
Accordingly, this invention provides, in one of its embodiments, a composition which comprises (I) n-propyl bromide having dissolved therein (ii) an ether, preferably a cyclic diether having a 5- or 6-membered ring, and most preferably 1,3-dioxolane, and (iii) an epoxyalkane having in the range of 3 to about 7 carbon atoms in the molecule, preferably 1,2-epoxybutane, in proportions such that said composition is nonflammable under the conditions of ASTM test procedure D 3065 using 1-fluoro-2,2,2-trifluoroethane as the propellant.
Another embodiment of this invention is a method of reducing the flammability of n-propyl bromide in aerosol applications (when tested under the conditions of ASTM test procedure D 3065 using 1-fluoro-2,2,2-trifluoroethane as the propellant), which method comprises blending with the n-propyl bromide (i) in the range of about 0.1 to about 1 wt % of an ether, preferably a cyclic diether having a 5- or 6-membered ring, and most preferably 1,3-dioxolane, and (ii) in the range of about 0.02 to about 0.5 wt % of an epoxyalkane having in the range of 3 to about 7 carbon atoms in the molecule, preferably 1,2-epoxybutane. Said weight percentages are based on the total weight of the n-propyl bromide and components (i) and (ii). Preferably, the weight ratio of (i):(ii) is in the range of about 1:1 to about 5:1.
Still another embodiment of this invention is a stabilized solvent composition comprising a solvent portion which includes at least 90 wt % of n-propyl bromide and a stabilizer system consisting essentially of (i) in the range of about 0.1 to about 1 wt % based on the total weight of the composition, of an ether, preferably a cyclic diether having a 5- or 6-membered ring, and most preferably 1,3-dioxolane, and (ii) in the range of about 0.02 to about 0.5 wt % based on the total weight of the composition, of an epoxyalkane having in the range of 3 to about 7 carbon atoms in the molecule, preferably 1,2-epoxybutane. Said weight percentages are based on the total weight of the n-propyl bromide and components (i) and (ii). Preferably the weight ratio of (i):(ii) is in the range of about 1:1 to about 5:1.
As regards reduced flammability, when the above proportions of the flammable additives (the ether and the epoxyalkane) are blended into n-propyl bromide, and the mixture is combined with a component which functions as a propellant and utilized as an aerosol, the flammability of the resulting formulation can be significantly decreased relative to essentially additive-free n-propyl bromide combined with the same component that functions as the propellant. In addition, such proportions of the flammable additives provide effective stabilization against metal corrosion even though in preferred formulations the composition is devoid of a nitroalkane or a nitroaromatic hydrocarbon such as nitrobenzene. At the same time the efficacy of the composition as a solvent is maintained.
Pursuant to an additional embodiment, this invention provides a method for cleaning a surface which method comprises applying to the surface a composition in the form of an aerosol spray, such composition being comprised of solvent portion which includes at least 90 wt % of n-propyl bromide and a stabilizer system consisting essentially of (i) in the range of about 0.1 to about 1 wt % of an ether, preferably a cyclic diether having a 5- or 6-membered ring, and most preferably 1,3-dioxolane, and (ii) in the range of about 0.02 to about 0.5 wt % of an epoxyalkane having in the range of 3 to about 7 carbon atoms in the molecule, preferably 1,2-epoxybutane. Said weight percentages are based on the total weight of the n-propyl bromide and components (i) and (ii). Preferably the weight ratio of (i):(ii) is in the range of about 1:1 to about 5:1.
The above and other embodiments of this invention will be apparent from the ensuing description and the appended claims.
The compositions of this invention contain at least 90 wt %, preferably at least about 95 wt %, and more preferably at least about 98 wt % of n-propyl bromide. Most preferably the composition is formed from n-propyl bromide that has a purity of at least 99 wt %, where such wt % refers to percent of n-propyl bromide plus impurities, if any. n-Propyl bromide is available commercially from Albemarle Corporation of Richmond, Virginia, and from other commercial sources.
In the practice of this invention use is made of ethers that are soluble in the solvent portion of the composition. Thus, use can be made of aliphatic, aromatic and cyclic ethers, which can be either monoethers or polyethers that are suitably soluble in n-propyl bromide. Suitable ethers include, but are not limited to, diethyl ether, dipropyl ether, dibutyl ether, methyl tert-butyl ether, ethyl tert-butyl ether, tert-amyl methyl ether, anisole, tetrahydrofuran, tetrahydropyran, the methyltetrahydrofurans, and similar monoethers. Among suitable polyethers are such materials as 1,2-methoxyethane, the dimethyl ether of diethylene glycol, the dimethyl ether of triethylene glycol, the dimethyl ether of tetraethylene glycol, 1,4-dioxane, 1,3-dioxolane, 2-methyl-1,3-dioxolane, and an analogous polyether solvents. Particularly desirable ethers are cyclic diethers such as 1,4-dioxane and 1,3- dioxane, and especially 1,3-dioxolane and alkyl substituted 1,3-dioxolanes. Particularly preferred as the ether component is 1,3-dioxolane. The ether component is used in amounts ranging from about 0.1 to about 1.0 wt %, preferably in the range of about 0.2 to about 0.5 wt %, and most preferably of the range of about 0.3 to about 0.5 wt %. Said weight percentages are based on the total weight of the n-propyl bromide, ether, and epoxyalkane components.
The other additive component required in the compositions of this invention is an epoxyalkane having from 3 to about 7 carbon atoms in the molecule. Suitable epoxides include, but are not limited to, 1,2-epoxypropane, 1,2-epoxybutane, 2,3-epoxybutane, 1,2-epoxypentane, 2,3-epoxypentane, 1,2-epoxyhexane, 2,3-epoxyhexane, 4-methyl-1,2-epoxypentane, 1,2-epoxyheptane, 2,3-epoxyheptane, 3,4-epoxyheptane, cyclohexene oxide, glycidyl methyl ether, and the like. Preferred epoxides are the linear 1,2-epoxyalkanes having from 3 to about 7 carbon atoms in the molecule, and most preferred is 1,2-epoxybutane. The epoxide is used in amounts of about 0.02 wt % to about 0.5 wt %. Preferably the epoxide is used in an amount in the range of about 0.1 to about 0.3 wt %. Said weight percentages are based on the total weight of the n-propyl bromide, ether, and epoxyalkane components.
Preferred proportions of the ingredients in the compositions of this invention are 98.75 to 99.75 wt % of n-propyl bromide; 0.10 to 1.00 wt % of the ether component; and about 0.15 to about 0.25 wt % of the epoxyalkane component. Most preferred is about 0.15 to about 0.20 wt % of the epoxyalkane, e.g., 1,2-epoxybutane. Most preferably the n-propyl bromide has a purity of at least about 99%.
Other additives can be included in the compositions of this invention provided they do not materially detract from the flame suppressant or stabilization performance characteristics of the compositions. Preferably the compositions are devoid of any additive ingredient(s) other than one or more ethers and one or more epoxyalkanes (except for the propellant).
The aerosol containers with which the compositions of this invention are employed in aerosol spray applications are pressurized aerosol spray containers in which a propellant is used. Such devices are known and described in the literature. Any suitable propellant of relatively low flammability can be used to pressurize the aerosol spray container, such as, for example, fluorocarbons, fluorohalocarbons, fluorohydrocarbons, and fluorohalohydrocarbons with suitably high vapor pressures including bromochlorodifluoromethane, 1,1,1-trifluoroethane, 1,1,1,2-tetrafluoroethane, dichlorofluoromethane, dichlorodifluoromethane, chlorotrifluoromethane, trichlorofluoromethane, sym-tetrachlorodifluoroethane, 1,2,2-trichloro-1,1,2-trifluoroethane, and sym-dichlorotetrafluoroethane, and mixtures thereof. When using 1-fluoro-2,2,2-trifluoroethane as the propellant, the wt % ratio of 1-fluoro-2,2,2-trifluoroethane to the sum of the n-propyl bromide, the ether, and the epoxyalkane in the cleaning composition is preferably at least about 30/70. Said wt % ratio is most preferably in the range of about 30/70 to about 40/60.
The solvent compositions of the invention have particular utility in non-spark-free applications and environments as aerosol spray cleaning compositions. Preferably, the surface to be cleaned in the presence of potential ignition sources such as electrical switches or the like should be at a relatively low temperature such as from about 25xc2x0 C. to about 60xc2x0 C. The aerosol spray discharge is applied to the surface. The discharge functions as a cleaner, and is either removed, as by wiping with a cloth, or is allowed to drip off.
The following demonstrates the exceptional non-flammability and non-corrosiveness of the solvent compositions of this invention. The examples are not intended to constitute limitations on the invention, but rather are presented for purposes of illustration.